General practice in potash ore flotation aims at maximum recovery of coarse sylvite (KCl) particles. Depending on sylvite grain size, the potash ores are ground to either -6 mesh (3.36 mm) or -8 mesh (2.38 mm) and are classified into +20 mesh (0.85 mm) coarse and -20 mesh fine streams. In order to achieve maximum recovery of the coarse particles, these two are reagentized separately and then are usually floated together. The recovery of coarse potash particles is generally low.
Long chain primary amines are exclusively used by industry in the flotation of sylvinite ores. Extender oils, which are generally petroleum production heavy residue by-products, are used to assist the flotation of coarse fractions. Since these extender oils are usually carcinogenic due to their polycyclic aromatic components, much effort has been devoted to seek low carcinogenic replacements [J. S. Laskowski and Q. Dai, Proc. 18th Int. Mineral Processing Congress, Sydney, 1993].
Since the Krafft points of long-chain amines in brine significantly exceed temperatures at which commercial potash flotation plants operate (10.degree.-35.degree. C.), amines in brine appear in the form of colloidal species [J. S. Laskowski, Flotation of Potash Ores, Reagents for Better Metallurgy (P. S. Mulukutla, ed.), SME, Littleton, 1994, pp. 225-243] and the interaction of sylvite particles with such species determines flotation efficiency. To ensure good flotation, colloidal amine has to be well dispersed in brine.